Diaphragm chuck



oct. 5, v,1948.

G. HOHWART E T AL DIAPHRAGM CHUCK Filed July 13, 1946 VENToRs, 0

Patented Oct. 5, 1948 DIAPHRAGM CHUCK George Hohwart and Ernest F. Hohwart, Detroit, Mich., assignors to N. A. Woodworth Company, Ferndale, Mich., a corporation of Michigan Application July 13, 1946, Serial No. 683,459

This invention relates to diaphragm-chucks and has for its principal object the provision of'a chuck of this type including a novel feature of construction which increases the field of `adapt ability of a chuck of this type.

Objects of the invention include the provision of a diaphragm chuck, the diaphragm of which is so constructed and arranged as to permit a relatively greater iiexing of the diaphragm than in conventionally constructed diaphragm chucks of the same diameter without stressing the material of the diaphragm beyond its elastic limits; the provision of a diaphragm chuck in which the diaphragm is so constructed as to permit the chuck to receive workpieces having a greater tolerance in the dimensions of the surface to be engaged by the jaws of the chuck than in prior diaphragm chucks of the same size; the provision of a diaphragm chuck including a diaphragm which is corrugated in such a manner as to render the central portion of the diaphragm more flexible, thereby allowing it to be sprung or flexed to a greater extent than the diaphragms in conventional diaphragm chucks, and thereby to permit the chuck to receive workpieces having a greater tolerance of the chucking surface thereof than has heretofore been possible; and the provision of a diaphragm chuck including a diaphragm having jaws secured to the axially outer face thereof and 'corrugations formed in the diaphragm intermediate the jaws to enhance the flexibility of the diaphragm.

The above being among the objects of the present invention, the same consists Vin certain new and novel features of construction and combinations of parts to be hereinafter described with reference to the accompanying drawing, and then claimed, having the above and other objects in view. i

In the accompanying drawing which illustrates a suitable embodiment of the present invention and in which like numerals refer to like parts throughout the several different views,

Fig. 1 is a sectional View taken longitudinally through a diaphragm chuck incorporating the present invention, as on the line l-l of Fig. 2, and showing the same mounted upon the outer end of the machine tool spindle; V

Fig. 2 is a face view of the diaphragm chuck shown in Fig. 2; and Y Fig. 3 is an enlarged, transverse sectional View taken on the line 3-3 of Fig. 2 and illustrating a corrugation formed in the diaphragm ofthe chuck.

Diaphragm chucks conventionally `includea 5 claims. (C1. 279-46) metal diaphragm in the form of a fiat and plain bottomed cup or a flat, plain disk arranged with Y the general plane ,thereof perpendicular to the axis of rotation of the chuck and carrying workengaging Vjaws on the axially outer facey thereof. Means are provided for springing the central portion of the diaphragm axially out of its normally free position so as to effect either an expansion or contraction of the jaws, depending upon whether the jaws are adapted for internal or external chucking operations, to `permit the removal or introduction of the workpiece from or to the jaws,

upon which the pressure applied to the diaphragm is relieved thereby to permit the jaws to grip the piece ofwork as the diaphragm returns toward its normally free position.

In order to`grip a piece of work with su-icient rigidity and seoureness to permit a machining operation to be performed thereon, the diaphragm must be made sufficiently heavy or thick to withstand the stresses set up in the machining operation without yielding of the jaws on the workpiece gripped thereby, As a result, the amount which the diaphragm may be axially sprung without permanent -distortion thereof is relatively small, and in small and medium size chucks in particular the movement of the jaws away from work-engaging position has heretofore required that the surface of the piece of work which the jaws are to engage be held withina maximum tolerance of approximately ten one-thousandths of an inch. If

thechucking surface of the work is one which may be a rough machined surface, nevertheless, under such circumstances, the diameter of such ohucking surface must be held within a maximum tolerance of ten one-thousandths of an inch in order to enable such workpieces to be consistently grippedV in the chuck. As is well understood by those skilled in the art, the closeness of the tolerance on a machine surface has a direct bearing on the cost of machining such surface so that under the circumstances above mentioned, if the tolerance of the surface of theY workpiece which is to be gripped by the jaws in the chuck can be increased, the machining cost of the work can 4be correspondingly decreased. It is therefore desirable to provide` a diaphragm construction for a diaphragm chuck which will enable the diaphragm to be sprung out of its relatively free position to al greater extent than the diaphragms heretofore employed and without causing permanent de- The above described desirable attribute is ob.

tained in accordance with the present invention compared to a plain diaphragm, without permanently deforming the diaphragm. This means that a corresponding increase in the movementiof the chuck jaws is obtainable, and a corresponding increase in the permissible tolerance of the chucking surface of the work is likewise possible, with all the attendant advantages,

It will, of course, be understood that the present invention may be adapted to any-suitable design and/or construction of diaphragm .chuck, that shown in the drawing being shown merely by way of illustration. In this connection, it may be noted that the particular form of diaphragm shown in the drawing is ,disclosed and claimed 'in United States Letters Patent No. 2,403,599, issued July 9,1946. The particular jaw structure shown onthe diaphragm in the vaccompanying drawing forms the subject matter of our copending application for Letters Patent of the United States for improvements in Diaphragm chuck filed July '13, .1946, and serially Numbered 683,457. The fluid pressure operated means and vassociated mechanism shown in the accompanying drawing for effecting operation of the diaphragm is shown and claimed in our copending application for 'Letters Patent of the United States for improvements in `Diaphragm chuck, filed July 13, 1946, and 'serially Anumbered 683,458.

In the particular diaphragm chuck Vshown in th'efaccompanying drawing by way ofillustration, there is a disk-like mounting plate ormember l0 ypiloted upon the outer hanged end l2 -of the machine -t-ool spindle i4 and secured thereto by means of screws IB. The `axial-ly forward lfaceoi the :mounting `member' l0 is shouldered and receives concentrically Ythereon-a ring i8. A shoulderedfbacking-plate ispiloted `in the Abore of the ring i8 vand is lsecured to the axially outer face thereof by means of `screws 22. Screws 24 projecting rearwardly and inparallel relation 'with -respect'to the `axis of the-chuck through the mounting plate 2l! and ring I8, Vthread linto the I-rnounting'plate l0 to secure all of these parts together in Vunitary relationship. VThe particular diaphragm shown is of generally cup-shaped lconformation includinga1disk#likecentralportion 25 and -a rearwardly flanged marginal por-tion 23 which-fits over the periphery of Ithe'backingplate 20, and While it may -be 'suitably fixed thereto by a-nysuitablemeans it is preferably vsecured thereto 'by brazing or welding as disclosed and Vclaimed lour y-copending application for .Letters Patent of the United States for Yimprovements in Diaphragm chuck. filed July '13, 11946, and serially numbered 683,456.

The chuck may, -of course, be :equipped `with any desired number of jaws -or'jawlde-viceaiour of the same being shown in 4theidrawing by v.way -of illustration, and these being equally angularly spaced with respect to each other about -the axis of the chuck. Each jaw device for assembly comprises Va radially extending Vjaw `hase Sil suitably-fixed to the axially louter vface of the-central portion 26 of the diaphragm, and each jaw 'base @il -is provided with 'a radially extendingdovetail groove in `.its axially outer face.` `Each jaw'base 13S' receivesa Ajaw 32 provided with a r.dovetail rib or bead on its-axially'innerface which is received inthe groove of the 'base-.30 in interttingrrelation `with `respect thereto. The axially `inner edge of each jaw 32 is laterally flexible and may be spread by means of setscrews 34 so as to bind in the dovetail groove of the base 30. Radially outwardly of each jaw 32, a backing-up member 36 is located and which is provided with a dovetail rib or bead on its axially inner face interiitting the groove of the jaw base 30. Each backing-up Vmember 3,6.is ,secured inplace `on the jaw base 30 by means of a setscrew 38, the inner end of which is received in one of four depressions 40 provided in the bottom of the groove in the jaw base 30. An adjusting s'crew 42 threaded radially through each backing-up member 36 extends into contact with the radially outer face of the corresponding jaw 32 andis locked in adjusted position by means of a locknut 44. The adjusting screw 42 extends in blocking relation with respect to the outer end of the setscrew 38 so as to prevent setscrew 38 from becoming disengaged from its corresponding depression 40, thus providing a positive mechanical lock for the setscrew llil. As 'previously mentioned, .this jaw mechanism forms no part of the .present invention, but comprises Ythe 'subject matter lof our copending Aapplication Vfor Letters Patent of the United .States for improvements in Diaphragm chuck, `iiled July 13, 1946, and serially numbered 683,457.

The diaphragm 26 is .operated-to openthe jaws 32 to receive a Ypiece of work `therein in the `following manner. The ring i8, Awhich spaces the mounting 4plate Id yand backing plate 2B, interiorly forms a cylinder in vwhicl'i a piston 5i) is reciprocally received. rI-he backing plate 2-0 -is imperforate except for -a central opening :52 -in which a sleeve member fdd is -axiaflly slidably'received `in `concentric vrelation with 'respect to lthe axis of .the chuck. "Ii-he sleeve-56 is Iof such length that :its-rear end abuts Zthe forward face -o-f the piston 5i? 4and its' forward-end abuts vthefrear lace of Athe diaphragm 26. vrllhediaph-ragm 2651s pref- .erably Lprovided Iwith -a central aperture '.56 of the same size yas the bore of Ithe sleeve 54 so as to permit work -to be vprojected to 4within-the sleeve 54 when necessary for proper chucking l.operai-,ions thereon.

The `particular chuck shown by lway of illustration being adapted for externally l chucking 1a pieceof lf-work, Vthen liu-id under pressure is introduced between Ithe rear :face of the ypiston 50 and the 4forward face -of the mounting member YIll to eiiectmovement of the piston 5D and, throughfthe sleeve 54, a corresponding movement of :the centrai portion of Ythe diaphragm Y26. -It will, of

course, Vbe appreciated that where the chuck is adapted lfor inter-nal -c'hucking operations, Athen -a different -form of means, such as shown and'described in our vcopending applications above identied, may be employed to -etrect axially rearward movement of the central portion of the diaphragm '23 vwith the -piston 50. ln the flatter case it Lwill, of course, be appreciated that -uid'under'pressure lwill have to-be introduced between-the axially outer face-.of the piston 50 and the :rear -facejef the backing .member '20, all -oi'wlhich may be accomplished in the manner disclosed in our 'copending applications above identified. In the particular case shown, A-'u'id under Apressure-is introduced behindlthe-piston'S93-through a tube-or pipe` 58f threaded into anopening-150m themounting member I0 and extendingeto a-suitable source of -uid vunder pressure. Thus, -w-hen 'uid under pressure is introduced through the pipe SBitacts on the axially inner fface `of the piston '50 and urges the same axially outwardly, and the #force of this -pressure is transmitted vthrough nthelsleeve 54 to the central portion of the diaphragrmcausing the central portion of the diaphragm to be spread so as to permit the removal of a piece of work from between them, or the introduction of a piece of work to between them.

Now as previously explained, it has been the conventional practice to form a diaphragm such as the diaphragm or its equivalent as a substantially flat and plain disk, and becauseof this form, the amount which the central portion of the diaphragm may be sprung axially in order to move the jaws to release or receive a piece of work Without exceeding the elastic limit of the material from which the diaphragm is formed and therefore without permanent distortion of the diaphragm, has been relatively limited, requiring the surfaces of the workpiece which are to be engaged by the jaws of the chuck to be held within relatively close limits. In accordance with the present invention, in order to increase this flexibility of the diaphragm so as to permit its central portion to be sprung to a greater extent and therefore permit greater relative movement between the jaws of the chuck to release or receive a piece of work without permanently distorting the diaphragm, the diaphragm 20 is corrugated in such a manner as to increase its flexibility as compared to a conventional diaphragm of the same diameter and thickness, While such corrugations may be provided in a number of different arrangements and placement, and the number of corrugations employed varied to a considerably great extent, in the drawing, by way of illustration, one corrugation 'i9 is centrally provided between each pair of chuck jaw assemblies, and extends radially with respect to the axis of the chuck. The particular corrugations 70 shown are of maximum depth at their axially inner ends, namely, at the bore 56, and fade out substantially at the junction of the central portions 2,5 and marginal portions 28 of the diaphragm. In other words, the corrugations 'I0 are of greatest extent at the central portion of the diaphragm Iwhere the greatest amount of axial movement occurs, and their depth or extent varies substantially in accordance with the corresponding ilexibility required at different radial positions of the diaphragm. Such arrangement will ordinarily be found most desirable and constitutes a more lim- .ited phase of the present invention. For the purpose of facilitating the design and machining of the jaw bases 30 and their securement to the diaphragm 26, the corrugations 10 preferably do not extend into the area of the diaphragm to which the jaw bases 30 are secured, but, of course, may where this is found to be either necessary or desirable to obtain the desired flexibility of the diaphragm. l

It will be appreciated that the provision of the corrugations 10, or their equivalent, permit a greater exing of the central portion of the diaphragm without exceeding the elastic limit of the material from -which it is constructed than is the case where such corrugations are omitted, and that, therefore, they permit a greater flexing of the diaphragm than is possible with conventional at diaphragm without permanent deformation thereof, resulting in greater movement of the jaws and consequently permitting workpieces having greater tolerances to be successfully chucked therein.

i flexed outwardly and causing the jaws 32 to be ,phragm arranged with the general plane of thickness thereof perpendicular to the axis of rotation of said chuck, said diaphragm having radially directed corrugations therein serving to increase the flexibility of said diaphragm axially of said chuck, and jaw devices iixed to the outer face of said diaphragm each between an adjacent pair of said corrugations. e

3. In a diaphragm chuck, in combination, a diaphragm arranged with the general plane of thickness thereof Vperpendicular to the axis or rotation of said chuck, angularly spaced jaw members iixed to the axially outer face of said diaphragm, said diaphragm having a central aperture therein and radially directed corrugations extending radially from said aperture between said jaw members, said corrugations being of greatest depth at said aperture and decreasing in depth radially outwardly therefrom.

4. In a diaphragm chuck, in combination, a diaphragm arranged in a general plane of thickness perpendicular to the axis Iof said chuck and rigidly secured with respect to the remainder of said chuck at its periphery, and a plurality of jaw devices secured to the axially outer face of said diaphragm, said diaphragm being radially corrugated with a corrugation extending radially between each adjacent pair of jaw devices.

5. In a diaphragm chuck, in combination, a diaphragm arranged in a general plane of thickness perpendicular to the axis of said chuck and provided with a central, axial opening therein, a plurality of jaw devices mounted on the axially outer face of said diaphragm in approximately equally angularly spaced relation with respect to each other about the axis of said chuck, said diaphragm having a radially directed corrugation therein between each adjacent pair of said jaw devices and extending from said central opening radially outwardly therefrom, whereby to increase the ilexibility of said diaphragm in an axial direction at its center.

GEORGE HOHWART. ERNEST F. HOI-IWART.

REFERENCES CITED The following references are of record in the iile of this patent:

UNITED STATES PATENTS 

